Problems are observed by strokes of lightning striking wind turbine rotor blade tips. Different know solutions to the problem are known. Common to the solutions is the risk of de-lamination or incineration of the surface composite material and/or heating and melting of metallic components. There is also the risk that shock waves, caused by internal arcs, may explode the blades, ripping the blade surface shells apart along the edges and from the internal carrying spar.
WO2005/026538 describes a method of lightning-proofing a blade on a wind-energy plant. The blade comprises a blade shell configured essentially as a fibre-reinforced laminate, which laminate comprises electrically conductive fibres. The blade comprises at least one lightning arrester configured for conducting lightning current, including preferably to ground. The electrically conductive fibres are connected to each other, and that at least one metallic receptor is arranged for capturing lightning current at or in proximity of the external face of the blade. The receptor and the fibres are connected to the lightning arrester for equalising the difference in potential between the lightning arrester and the electrically conductive fibres.
The document discloses that when the electrically conductive fibres are connected to each other, the fibres will cooperate on the conduction of a possible lightning current to prevent the current from running in individual fibres. The metallic receptor will simultaneously serve as the primary lightning capturing device and reduce the risk of lightning striking the laminate. The receptor being connected to the lightning arrester, the current will be conducted to ground, while the risk of transfer to the laminate is minimised in that a possible difference in potential between fibres and lightning arrester has been equalised. The document does not address the specific problems at the tip of the blade.